Using historical climate observations to understand future climate change crop yield impacts in the Southeastern US

Historical weather data (1900–2000) of the Southeast U.S.A. was divided into baseline (neutral, 1981–2000), warm (1935–1954) and cold (1958–1977) periods and used in impact simulation experiments to understand climate effects on a summer and a winter crop. Simulated summer crop (maize) yields were lower in the warm than the cold period, but also low during a neutral period. Simulated winter crop (wheat) yields were higher during the neutral period than during the warm and cold periods. A higher average temperature of a given period did not necessarily translate to lower crop yields. Specifically, the summer crop (maize) experienced about 7 % reduction in growing season length per degree increase in mean air temperature, and about 5 % for the winter (wheat) crop. Overall, the simulated maize yield was reduced by 13 % and wheat yield by 6.5 % per unit of increase temperature. In conclusion, simulated yield reduction per unit increase in mean temperature was reduced during the neutral period for the summer while for the winter crop there were fewer differences between the warm and neutral periods. The summer crop was sensitive to changes of mean growing season temperatures while the winter crops was sensitive to changes in CO₂.